VSRA Hang Your Machine Weekend

[asra]

Yes it is a Cop issue, and vertical Cop issues can very simply be fixed with an adjustment of your HS.Dint confuse the two Sam.Center of pressure is different to the airscoop I"m talking bout.A machine thats CLT and has the TL centered in the pressuer can still Java nose down tendency if the front area is Acton like an airscoop.And yes, adequate Hess will counter it, but very inefficiently.Definitely no confussion. Centre of pressure, is exactly what it sounds like.It acts on your gyroplane in all 3 axis (pitch, yaw, & roll) Its position is usually different dependant on the axis. Ideally, the CofP should be positioned close as possible to the machines CofG in pitch and roll only. In the Yaw axis the CofP should be positioned well behind the machines CofG. Regards SamL...............

[birdy]

Mate, your still not getn it Sam.Even COP isnt as simple as it sounds.Iv heard of maken a cardbord cutout of the frunt view of your machine and figuren the " average" [ for want ofa better word]

[asra]

Mate, your still not getn it Sam.Even COP isnt as simple as it sounds.Iv heard of maken a cardbord cutout of the frunt view of your machine and figuren the " average" [ for want ofa better word]

[birdy]

No Birdy, your wrong again,So your sayn COP and deflected air is the same thing?I think not.COP is the center of airodynamic drag in a given direction. [ in this case, horisontaly, and opposing the prop thrust]Deflected air applies a force in any direction except against prop thrust. [ in this case, the screen deflects air up, so the reaction is to push the nose down. It could be mounted 3" above the TL but it still applies a down force.]A virtical frunted screen could be centered so"s its COP is in line with thrust, and wont deflect any air up.But a screen with the zact same area but slopen back, also centered to the TL, will drive the nose down. It wouldnt matter where this screen is mounted in relation to the TL, it will always apply a down force.

[Tsemler]

I believe that Birdy is talking about parasite drag caused by the windscreen on the pod deflecting air upwards, therefore making it pitch down, if that’s the case it should pitch down more and more as he get faster? I believe, does it Birdy?A low COP Below the CG will all so have the nose in a down ward pitch, due to COP rotating around the CG. So if im understanding this right, if your got a windscreen on ya pod that is deflecting airflow upward you will need to have a COP higher than your CG to counter act the downward pitching of the windscreen airflow drag? Yeah?But really who give a **** if ya can get it close enough I reckon that’s good enough, coz it will never be the same during a flight anyway or with different loads.

[aussie_paul]

Isn"t a C of P the horizontal resultant of averaging all the drag forces acting on the machine at that particular moment?Aussie Paul.

[birdy]

Isn"t a C of P the horizontal resultant of averaging all the drag forces acting on the machine at that particular moment?Zactly PB.Nuthn to do with deflection, coz deflection isa different animal with different effects, but basicaly the same result.[ geez, its a while since we ever agreed on sumthn init?] if that’s the case it should pitch down more and more as he get faster? I believe, does it Birdy?Yup.So if im understanding this right, if your got a windscreen on ya pod that is deflecting airflow upward you will need to have a COP higher than your CG to counter act the downward pitching of the windscreen airflow drag? Yeah?Depends on how much deflection there is as to how much balance it needs.Most would need the COP to be too high to be practical.Itd be more practical to balance witha HS.And the more balance it needs, the more inefficiant it gets.Better to get rid of the down force to start with.

[chook]

Excellent discussion fellas.Just to give you an idea of the drag forces you"re dealing with, here are some figures from "average helicopter" profiles as described by Simon Newman in his book Foundations of helicopter flight. As a percentage of the total drag, the fuselage only presents 13%, the HUB - a whopping 20% (this applies to your average Bell 206, Sik 76 etc), antennae = 13%, skids = 8% and so it goes. It also describes induced drag of above 3 degrees nose down of 2.5% and this is the figure that Birdy is eluding to with his windscreen deflection - except that with our gyros its there permanently not when you have a nose down situation.

[aussie_paul]

Isn"t a C of P the horizontal resultant of averaging all the drag forces acting on the machine at that particular moment?Zactly PB.Nuthn to do with deflection, coz deflection isa different animal with different effects, but basicaly the same result.[ geez, its a while since we ever agreed on sumthn init?]Birdy, isn"t deflection just another part of all the drag components?Aussie Paul.

[birdy]

No PB. The only thing it has in common with the COP is the effect on the machine the pilot feels.Center of pressure below the TL will pull the nose down.Upward deflection pushes the nose down.Both are amplified with increased AS.But deflection happens with very minimal drag.Drag happens with very little deflection.The direction of the 2 forces are 90* apart. [ drag pulls back, deflection pushes down]Drag rotates the machine round the TL at power.Deflection is happeing any time theres AS, power on or not.

[aussie_paul]

No PB. The only thing it has in common with the COP is the effect on the machine the pilot feels.Center of pressure below the TL will pull the nose down.Upward deflection pushes the nose down.Both are amplified with increased AS.But deflection happens with very minimal drag.Drag happens with very little deflection.The direction of the 2 forces are 90* apart. [ drag pulls back, deflection pushes down]Drag rotates the machine round the TL at power.Deflection is happeing any time theres AS, power on or not.I can"t quite see that Birdy. All aerodynamic info I have been exposed to since l learnt to fly GA in 1965 has never mentioned "deflection". Doesn"t the drag rotate the machine around the CoM? Isn"t what you are calling deflection just a component of all the drag forces acting at that moment in time as I said above? I can"t see that you can say that drag and deflection are 90 degrees apart. Isn"t it the resultant that counts?Folks, what am I missing here?Aussie Paul.

[birdy]

PB, the opposit and equal reaction on the frame to drag is a force that pulls the machine against the direction its traveling.The oppoiste and equal reaction of deflection [ off a screen] is down.Think of the tail ona F1 car, that airscoop thing hangn off its ass.Wot dose that do?It aids traction of the drive tyres by forcen them into the road wen they have sufficiant air speed. If that wasnt there, theyed never be able to use all those zillions of HP without smoken the tyres.How dose that tail push the ass down? By deflecting air up, same asa slopen screen ona gyro.And you can hava a deflecter thats very efficiant at pushn air up without much drag at all.Drag is the effect on the air that any airborn object has on the air its traveln through, through the friction it has with the air. If you watch a car driven down a dusty road, you can "see" this effect as the air and dust are sucked along for a distance behind it.You mite have seen sum F1 raceing in TV wen its wet. Take note of the water spray behind one at speed. Them suckers deflect air [ and spray] 20 odd feet up.Drag and deflection have basicaly the same effect ona gryo, but by different means.

[bones]

I see so now now a race car driver, multi-taltened sucker arent you

[kingo]

hey birdy i thought dat d flection was what ya see in mirror. ;D also found this, seems f1 have trouble d flection

[aussie_paul]

PB, the opposit and equal reaction on the frame to drag is a force that pulls the machine against the direction its traveling.The oppoiste and equal reaction of deflection [ off a screen] is down.Think of the tail ona F1 car, that airscoop thing hangn off its ass.Wot dose that do?It aids traction of the drive tyres by forcen them into the road wen they have sufficiant air speed. If that wasnt there, theyed never be able to use all those zillions of HP without smoken the tyres.How dose that tail push the ass down? By deflecting air up, same asa slopen screen ona gyro.And you can hava a deflecter thats very efficiant at pushn air up without much drag at all.Drag is the effect on the air that any airborn object has on the air its traveln through, through the friction it has with the air. If you watch a car driven down a dusty road, you can "see" this effect as the air and dust are sucked along for a distance behind it.You mite have seen sum F1 raceing in TV wen its wet. Take note of the water spray behind one at speed. Them suckers deflect air [ and spray] 20 odd feet up.Drag and deflection have basicaly the same effect ona gryo, but by different means.Nah, I don"t think so Birdy. I believe the spray behind the race car is lifted up to the area of lower pressure created by the negative AoA of the aerofoil. I think deflection is just your name for one of the drag/lift components.Aussie Paul.